HQ-E爆破地震测深剖面的地壳浅部精细结构及其地质构造研究

THE FINE VELOCITY STRUCTURE IN THE SHALLOW CRUST ALONG THE HQ?E SEISMIC PROFILE IN SOUTHEASTERN CHINA

HQ E爆破地震测线的地壳浅部的精细结构研究结果表明 ,上地壳的速度结构由疏松盖层、沉积层、加里东褶皱构造层及元古宙结晶基底等 4个构造层构成 ,且大致以武夷山为界 ,宁都以西的低速凹陷区与中新生代沉积盆地相对应 ,加里东褶皱基底底部剧烈起伏 ,其最大埋深可达 10km ;而在宁都以东地区 ,地表速度明显增大 ,且加里东褶皱基底底界的深度明显变浅 ,仅为 3～ 5km。笔者根据地壳浅部速度精细结构的变化特征对剖面沿线的构造单元进行了划分 ,并对邵阳盆地、衡阳盆地、茶陵盆地及泰 (和 )兴 (国 )盆地等盆地的分布范围、性质。

This paper discusses the fine velocity structure in the shallow crust on the basis of the wide-angle seismic data collected along the HQ?E profile. The velocity structure depicts the characteristics of formation and development of the South China fold belt. The shallow crust is composed evidently of four strata: sedimentary cover, sediments, Caledonian fold basement and Proterozoic crystalline basement. The velocity structure shows obvious differences laterally along the profile. To the northwest of Wuyi Mountain (near Ningdu), the low velocity depression is correlated to the Mesozoic and Cenozoic basins, with strong relief up to a maximum depth of 10 km at the bottom of the Variscan fold basement. As for the velocity structure to the southeast of Ningdu, the velocity near the surface becomes much higher, and the bottom of the Caledonian fold basement gets thinner, merely 3～5 km in depth. At the end of this paper, the author makes a tentative analysis of several basins according to the fine velocity structure in the shallow crust.